'Then why don't you tell us the whole truth?'

'Give me the neurolectrin first.'

The Doctor shook his head. 'Not until you tell us everything, Oldeman. And I mean everything.' everything.'

'For pity's sake! Give me the neurolectrin!' Oldeman's eyes bulged. 'The potential damage to my brain would be irrevocable!'

'Irrevocable damage to your brain? I'll take that risk.'

' Will you?' Oldeman gasped.

'You may have the idea that I'm all fair play and scruples, Professor,' the Doctor went on, 'but I'm a very worried man and my concern for your continued good health comes quite low on my list of priorities at the moment. Now start talking.'

'All right, so the research project was was mine. Garondel was just a technician - bright enough in his own field but idealistic. I didn't have any time for him. He tried to sabotage my work at every stage.' mine. Garondel was just a technician - bright enough in his own field but idealistic. I didn't have any time for him. He tried to sabotage my work at every stage.'

'It's a pity he didn't succeed,' said Tegan sourly.

'He was a young fool! I was on the cusp of a real breakthrough! The creature was created from a genetic blueprint we calculated using Akoshemon DNA. I truly believed that the study of this specimen would bring tremendous benefits to the field of suspended animation and gene manipulation. But almost as soon as we had generated the creature, I realised it was something special! special! I had created a new, completely unique life-form!' I had created a new, completely unique life-form!'

'And so you set it free.' said the Doctor.

'I had to see what it could do, what its instincts would be.

Don't you understand?'

'I understand that you are an egotistical fool, Professor Oldeman,' the Doctor said. 'There was never any sign of the creature having broken out of its generation chamber. It must have been released.'

'Why did you lie to us?' asked Tegan.

Oldeman looked desperate. 'What else could I do? The creature was uncontrollable - a savage. It killed everyone else. I barely escaped it, and then only by hurling myself into an experimental stasis tank for goodness knows how long.

One hundred and sixty years, as it turned out and that wasn't long enough!'

'But why didn't you tell us who you really were when we woke you up?' Tegan asked.

'Would you have done?' Oldeman sagged. 'I knew there was a good chance whoever found me in the stasis tank would have checked the computer files first. I took the precaution of altering the scientist ranking in the hope of escaping the blame when I was found.'

'Meanwhile the creature has followed the genetic instincts you were so keen to observe,' said the Doctor.

'Instincts that were coded right into its very unique DNA.'

'I don't understand,' Oldeman said.

'No, you wouldn't,' the Doctor responded. 'Professor Oldeman, your blind arrogance has released a creature whose only instinct is to obtain human blood and bile for the thing thing it serves.' it serves.'

'Thing? What thing? I don't understand!'

'The creature drained its victims of their blood for use in the revitalisation of an ancient evil, buried at the centre of this moon.'

'What? How do you know all this?'

The Doctor straightened up and pushed his hands into his pockets. 'I really don't have the time to explain it all to you, Professor,' he said.

'Come along, Tegan, we'll have to see Captain Lawrence.'

'Wait a minute,' Oldeman said, sitting up. 'What about my neurolectrin?'

The Doctor stopped on his way to the exit and tossed the injector to Oldeman, who caught it. 'But it's empty!'

'I know,' the Doctor said. 'I gave you the dose just before you woke up.'

Silas Cadwell watched the Doctor and Tegan leave the medical bay. They didn't see him lurking in one of the recessed doorways further along the corridor. Cadwell waited until they had disappeared from view and then entered the sickbay unseen.

'What do you want?' snapped Oldeman, sitting up and glaring fearfully at the 2IC.

'Go back to sleep,' Cadwell told him, following the instruction with a a ferocious blow to the man's head with the b.u.t.t of his gun. Oldeman fell back onto the bed, stunned and bleeding. ferocious blow to the man's head with the b.u.t.t of his gun. Oldeman fell back onto the bed, stunned and bleeding.

Cadwell then walked over to the couch where Nyssa lay.

He pressed the cold metal of the gun barrel against her temple. 'And you,' he said.

'Wake up.'

'This is unbelievable,' said Lawrence as he studied the data screen. It was full of information concerning the demonic history of the planet Akoshemon. 'Cadwell's working to his own personal agenda. He's a Consortium man in name only.'

'In some ways, then, you have to admire him,' Stoker said.

'Don't be facetious. Why has Cadwell brought an entire historical tract on the planet Akoshemon with him?'

'That's a very interesting question,' said the Doctor, walking into the cabin behind them.

Lawrence whirled around. 'What the devil! How did you get in here?'

'What's going on?' Stoker asked.

'That's what we're trying to find out,' Tegan told her.

'What have you found here?' asked the Doctor.

Stoker said, 'Silas Cadwell's a rogue Consortium officer, would you believe it. He's engineered this entire trip: according to his personal files, he's something of an expert on Akoshemon.'

The Doctor frowned. 'Is he really?'

'It's all in here,' Stoker said, tapping the puter 'He keeps everything locked away in a file called The Dark.' The Dark.'

'The Dark?' The Doctor looked eagerly from Stoker to Lawrence and back. Are you sure?'

'According to this, Cadwell is an expert on Akoshemon mythology,'

Lawrence explained. 'This file concerned the legend of a terrible creature from that planet's vile history called "the Dark".'

'So Vega Jaal was right all along,' Tegan said. 'He said that was what Was waiting for us - the Dark!'

'Do go on, Captain,' urged the Doctor. 'This is fascinating!'

'It seems this Dark thing was destroyed and burnt to ashes thousands of years ago by a band of early s.p.a.ce travellers.'

'Yes, I've recently read a similar account of the story,' the Doctor said.

'Written as a warning on the entrance to its burial crypt, right at the heart of this very moon.'

Lawrence and Stoker both stared at him, and the Doctor quickly explained where he and Nyssa had been and what they had found. When he had finished, Lawrence in particular looked horror-struck. 'It seems I was wrong to doubt you, Doctor. And doubly wrong to trust my 21C.'

'But what exactly is Cadwell up to?' Tegan asked.

'The best person to ask would be Cadwell himself,' the Doctor said. 'I'll call him in,' Lawrence said, reaching for the ship's intercom.

'No, wait,' Stoker said quickly. 'If he gets suspicious you'll only scare him off. Find out where he is and then we can we can go and see go and see him.' him.'

Nyssa stared at the muzzle of Cadwell's gun. 'What do you want?' she asked weakly.

'Get up,' Cadwell said. 'We're going on a little trip.'

'I don't understand. Where do you want to go?'

'I want you to take me to the same place you took the Doctor.'

Nyssa shook her head. 'Oh no. I'm not going back there.'

'Yes you are' Cadwell c.o.c.ked the pistol loudly. 'This is a DSA gun. It's not registered to my name and it won't show up on any of the ship's on board scanners, because they are calibrated to detect phased energy weapons only. No one knows I'm here and if I shoot you no one will suspect me.

Now do as I say.'

'I'm too ill...'

'Like I care.'

'I can hardly walk!'

'Let's put that to the test, shall we?' Cadwell jammed the barrel painfully into Nyssa's throat.

She took a series of deep breaths to steady her nerves, and then said, 'If you shoot me I won't be able to take you anywhere' Cadwell smiled. 'I don't have to shoot to kill' Slowly he lowered the gun down her neck, over her chest and then across to her right arm. The flesh on her upper arm quivered as the cold metal brushed against it. 'In fact I'd rather not shoot at all. But if you make me I will not hesitate.'

'All right,' Nyssa said carefully. 'Let me stand up.'

She clambered down from the medical couch and straightened up with as much dignity as she could muster.

Cadwell slipped behind her and rested the gun against her hip. Nyssa knew that any projectile fired from this range would cut right through the flesh and probable chip her pelvic bone, but it would not disable her.

Swallowing with difficulty, she said, 'You wish me to take you to the pit?'

'Yes.'

'Then you're more of a fool than even the Doctor thinks you are You can't possibly understand what's waiting there.'

'You'd be surprised.'

'You're mad'

'Maybe, maybe not,' Cadwell said with shrug. 'But I am am in a hurry so move!' He reached up with his free hand and caught a fistful of Nyssa's hair, twisting it until he had her bent backwards and gasping in pain. in a hurry so move!' He reached up with his free hand and caught a fistful of Nyssa's hair, twisting it until he had her bent backwards and gasping in pain.

Then, still holding the gun against her waist, he pushed her roughly towards the exit.